Double strut transmission housing structure for marine propulsion systems

Abstract

This invention provides a heat dissipation system for belt-driven and chain-driven prime movers. [Solution] The invention includes a cowling surrounding the prime mover, and first and second struts fixed to the cowling, each of which has a front portion, an internal belt space, and a rear portion, and further includes a lower unit coupled to the distal end of the strut, a sprocket rotatably disposed within the lower unit, a shaft rotatably coupled to the sprocket, and a belt rotatably connecting the drive shaft to the sprocket, wherein a first portion of the belt is located within the internal belt space of the first strut, and a second portion of the belt is located within the internal belt space of the second strut, and further includes a thermal circuit (having a heat transfer fluid) extending from the cowling through each strut into the lower unit.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 031,979, filed on May 29, 2020, and the entire content thereof is incorporated herein by reference.

[0002] Field of the Disclosure The present disclosure relates to marine propulsion systems, particularly to a housing structure for power transmission between a prime mover and a propeller shaft.

Background Art

[0003] Marine propulsion engines have historically been classified into three general types. Namely, an inboard marine propulsion system, an outboard marine propulsion system, and a stern drive or in - outboard marine propulsion system.

[0004] An inboard propulsion system has a prime mover that uses an energy source to convert energy into rotational motion of one or more shafts, and a transmission that transmits the rotational force to a propeller shaft protruding from the bottom of the hull. The propeller is attached to the end of this underwater shaft and generates thrust, which is usually directed by a rudder located on the stern side of the propeller. An outboard motor generally has a powerhead that houses the prime mover, a lower unit, or a gearcase that houses the propeller and shaft, and an intermediate section that provides a physical connection between the powerhead and the lower unit while allowing a transmission to transmit power from the prime mover to the propeller shaft. The entire outboard motor is assembled to the transom of the boat and can be removed. A stern drive system, also called an in - outboard system, houses the prime mover inside the boat. The shaft of the prime mover is connected to a transmission of an outdrive that transmits power to a lower unit or gearcase.

[0005] Sterndrive and outboard motor-type marine propulsion systems traditionally use a set of right-angle bevel gears to transmit rotational force from the prime mover to the propeller. In the case of combustion engines, an additional set of gears is used to allow rotation in the opposite direction.

[0006] A variety of power transmission methods, including belt or chain drive mechanisms, are known from the prior art. Synchronized belts have become robust and durable, making them suitable for use in higher-power marine engine transmission systems. Implementing such existing belt technologies presents challenges in terms of physical housing arrangement and mechanical assembly. The frontal area and hydrodynamic shape of the subwater portion of a marine propulsion system have a significant impact on the system's drag and efficiency. Adapting belt drive technologies with conventional physical structures designed to accommodate rotating shafts and gears is an obstacle to an overall efficient design. Embodiments of this disclosure are intended to address the aforementioned and other challenges.

[0007] overview The purposes and benefits of the disclosed subject matter are stated in the following description, will become apparent therefrom, and will be learned through the practice of the disclosed subject matter. Additional benefits of the disclosed subject matter will be realized and achieved by the methods and systems specifically indicated in the described specification and claims and the accompanying drawings.

[0008] To achieve these advantages and other advantages, as well as advantages in accordance with the purpose of the disclosed subject, the disclosed subject includes a marine propulsion system as embodied and broadly described. The marine propulsion system includes a first strut and a second strut, each of which has a front portion, an internal belt space, and a rear portion, with the first strut aligned with the second strut and the first strut separated from the second strut, and a lower unit coupled to the distal ends of the first and second struts, the lower unit having a nose portion, a middle portion, and a tail portion, and a sprocket rotatably disposed within the lower unit, and a sprocket rotatably coupled to the sprocket The device includes: a shaft that is concentric with the sprocket and has a front side extending to the front of the sprocket and a rear side extending to the rear of the sprocket; a belt that rotatably connects the drive shaft to the sprocket, with a first portion of the belt located in the internal belt space of the first strut and a second portion of the belt located in the internal belt space of the second strut; and a thermal circuit that extends from the cowling through the first strut and the second strut and into the lower unit and has a heat transfer fluid configured to flow through the thermal circuit.

[0009] In some embodiments, the first strut and the second strut have complementary shapes.

[0010] In some embodiments, the space between the first strut and the second strut is uniform over the length of the first and second struts.

[0011] In some embodiments, the thermal circuit is located within the front portions of the first and second struts, respectively.

[0012] In some embodiments, the thermal circuit is bidirectional, passing through the first strut and the second strut, respectively.

[0013] In some embodiments, the thermal circuit extends further through the middle portion of the lower unit.

[0014] In some embodiments, the thermal circuit extends further through the tail portion of the lower unit.

[0015] In some embodiments, plates are positioned at the proximal ends of the first and second struts, and the plates are substantially perpendicular to the first and second struts.

[0016] In some embodiments, the propeller is coupled to the rear side of the shaft.

[0017] In some embodiments, the lower unit has a nose cone and a tail fairing.

[0018] In some embodiments, the sprocket is located within the middle portion of the lower unit.

[0019] In some embodiments, the first and second struts are substantially linear.

[0020] In some embodiments, the first strut and the second strut each have an airfoil shape, where the leading edge of the airfoil corresponds to the front portion of the first and second struts, and the trailing edge of the airfoil corresponds to the rear portion of the first and second struts.

[0021] In some embodiments, at least one strut includes a removable trailing edge portion.

[0022] In some embodiments, one or more skegs may extend from the lower unit.

[0023] In some embodiments, at least one strut and the lower unit are formed as separate components from each other.

[0024] In some embodiments, the thermal circuit forms a closed-loop fluid path.

[0025] In some embodiments, the distal end of at least one strut is disposed in the middle portion of the lower unit.

[0026] In some embodiments, the internal belt space and the coolant circuit are separate passages from each other.

[0027] According to another aspect of the present disclosure, a marine propulsion device includes a first strut extending from a proximal end to a distal end and a second strut extending from a proximal end to a distal end, each of the first strut and the second strut having a front portion, an internal belt space, and a rear portion, the first strut being aligned with the second strut and the first strut being spaced apart from the second strut, the first strut and the second strut, and a lower unit coupled to the distal ends of the first strut and the second strut, the lower unit having a nose portion, a middle portion, and a tail portion, a sprocket rotatably disposed within the lower unit, and a shaft rotatably coupled to the sprocket and concentric with the sprocket, the shaft having a front side extending in front of the sprocket and a rear side extending behind the sprocket, and a belt rotatably connecting the drive shaft to the sprocket, a first portion of the belt being disposed within the internal belt space of the first strut and a second portion of the belt being disposed within the internal belt space of the second strut. A marine propulsion machine is provided.

Brief Description of the Drawings

[0028] [Figure 1] An isometric view showing an outboard motor according to an embodiment of the present disclosure. [Figure 2]A block diagram illustrating the component-level interaction between the entire propulsion system and the lower unit of the double strut according to an embodiment of the present disclosure. [Figure 3] A partial side view of the bullet-shaped structure of the double strut and lower unit, generally below the line 1-1 shown in Figure 1, according to an embodiment of the present disclosure. [Figure 4] A partial front view according to an embodiment of the present disclosure, showing generally below the line 1-1 shown in Figure 1. [Figure 5] A cross-sectional side view according to an embodiment of the present disclosure, showing generally below the line 3-1 shown in Figure 3. [Figure 6] A cross-sectional top view showing generally below the line 3-1 shown in Figure 3, according to an embodiment of the present disclosure. [Figure 7] A cross-sectional front view according to an embodiment of the present disclosure, showing generally below the line 3-1 shown in Figure 3. [Figure 8] A schematic diagram showing an outboard motor transmission system according to an embodiment of the present disclosure. [Figure 9] A schematic diagram showing a belt drive transmission system according to an embodiment of the present disclosure. [Figure 10A] A diagram visualizing the computational fluid dynamics of a double strut and a single strut according to embodiments of the present disclosure. [Figure 10B] A diagram visualizing the computational fluid dynamics of a double strut and a single strut according to embodiments of the present disclosure. [Figure 11] A graph showing the initial computational fluid dynamics drag results for a double strut (left) compared to a single strut (right) according to embodiments of the present disclosure.

[0029] Detailed explanation An outboard motor powertrain generally includes a prime mover such as a combustion engine or electric motor, a vertical drive shaft, bevel gears, a clutch, and a propeller shaft (to which the propeller is attached). Bevel gears are gears between two intersecting shafts, with the faces having the gear teeth being conical. Bevel gears offer higher efficiency than any other gear of choice and can allow for gear reduction between intersecting shafts. Clutches are used to allow the prime mover to move in one direction, but also allow the propeller shaft to rotate in both clockwise and counterclockwise directions. In various different embodiments, outboard motors may use a dog clutch for switching between forward, neutral, and reverse. A dog clutch requires the engagement and disengagement of a switching gear, which results in rapid wear on the gear teeth. To minimize this wear, the entire assembly may be submerged in oil or lubricant, which can be harmful to the environment and difficult to dispose of. Heat dissipation from key components, including but not limited to the prime mover, gears, and bearings, may be incorporated for reliable operation of this type of outboard motor. The outboard motor may draw in fluid (e.g., seawater) from a fluid body (e.g., the sea). Within this fluid body, the outboard motor operates to circulate the fluid around the system, cooling the components. However, this external fluid intake introduces contaminants, including but not limited to salt, sand, and / or mud, which can accelerate wear and corrosion processes. In some embodiments, the prime mover may be housed in a lower unit below the waterline. This configuration offers the advantage of simplicity but limits heat transfer capacity. In various embodiments, alternative means of power transmission include, for example, chain drive systems and belt drive systems instead of vertical drive shafts and bevel gears. In various embodiments, synchronous belts may be robust and durable, making them suitable for use in higher-power marine engine transmission systems.In various different embodiments, implementing such belt or chain technology presents challenges in physical housing arrangement and mechanical assembly, as the frontal area and hydrodynamic shape of the underwater portion of the marine propulsion system significantly impact the system's drag and efficiency.

[0030] Therefore, there is a need for marine propulsion systems optimized for belt-driven and chain-driven prime movers, while reducing drag (e.g., improving hydrodynamic quality) and improving heat dissipation. Embodiments of this disclosure are intended to address the above-mentioned and other challenges.

[0031] In various embodiments, a sterndrive or outboard motor-type marine propulsion system includes a prime mover that transmits power to a driven shaft via a synchronous belt, an anti-ventilation plate, a lower unit housing, one or more skegs extending from the bottom of the lower unit housing, and a set of struts (e.g., two struts) connecting the lower unit housing to mounting points on the anti-ventilation plate and cowling (and / or frame structure within the cowling). In various embodiments, the set of struts may be substantially aligned with each other (e.g., parallel). In various embodiments, each strut may include one or more (e.g., multiple) removable and modular trailing edge portions. In various embodiments, the removable trailing edge portions may allow for fine-tuning of the hydrodynamic properties.

[0032] In various embodiments, the mounting points connect the intermediate section to the lower unit and prime mover in the case of an outboard motor-type marine propulsion system, or to the lower unit and outdrive in the case of a sterndrive-type marine propulsion system. In various embodiments, certain variable parts of the system allow for lower drag, higher performance, and more efficient adaptation of belt drive technology. In various embodiments, the components of the marine propulsion system may be modular, interchangeable, and / or configured to have integrated cooling passages. In various embodiments, incorporating heat dissipation functions into a multi-strut (e.g., double-strut) structure can provide an increased surface area by the multi-strut, thereby optimizing heat transfer capacity. In various embodiments, a multi-strut (e.g., two struts) increases the surface area of ​​the struts in contact with water, thereby improving heat transfer (e.g., conduction) with water (similar to heat transfer of fins).

[0033] In various embodiments, the frontal area and hydrodynamic shape of the underwater portion of a ship's propulsion system can affect the system's drag and efficiency. Reducing drag in a ship's propulsion system directly improves the system's net efficiency. In various embodiments, a set of struts may be submerged in water during use, and the set of struts may have any suitable hydrodynamic shape, thereby reducing and / or optimizing drag. For example, each strut may include an airfoil shape, with the leading edge of this airfoil corresponding to the front side of the strut.

[0034] During operation, the belt generally has a taut side and a slack side. In various embodiments, the belt may be insulated (i.e., sealed) from the body of water surrounding the engine in which it is operating. In various embodiments, both sides of the belt may be supported to provide tension to the belt. In various embodiments, tensioning the belt can reduce (e.g., block) contamination from the surrounding water. In various embodiments, the marine propulsion system may include, among other things, a transmission of a continuous loop. For example, the engine may be mechanically (e.g., rotaryly) connected to the propeller via a belt or chain.

[0035] In various embodiments, each strut may be positioned at a predetermined distance from one another, thereby allowing fluid flow between the struts. For example, in a double strut configuration, the struts may be positioned between approximately 2 inches and 24 inches apart. In various embodiments, the struts may be positioned between approximately 1.5 inches and 6 inches apart. In various embodiments, for larger applications (e.g., yachts, tugboats, etc.), the struts may be positioned several feet apart. In various embodiments, the struts may be positioned up to approximately 12 feet apart. In various embodiments, the spacing of the struts may depend on one or more performance factors, such as (1) hydrodynamic interaction between struts and / or (2) hydrodynamic drag of the lower unit. In various embodiments, as the struts become wider, less fluid interaction (interference) may occur between multiple struts. In various embodiments, wider struts can improve certain performance factors. In various embodiments, the size of the lower unit (e.g., drag area) can be minimized, thereby minimizing drag. In various embodiments, the size of the lower unit can be minimized by providing a small frontal area of ​​the lower unit. In various embodiments, the size of the lower unit may be proportional to the size of the strut. For example, a larger lower unit may be provided for wider struts. In various embodiments, the struts do not have to be parallel to each other. For example, the struts may be nonlinear or arranged at a predetermined angle (e.g., a "V" shape) with respect to the horizon (sea level).

[0036] In various embodiments, each strut may include a vertical strut cross-sectional profile that minimizes water drag. In various embodiments, the cross-sectional profile can reduce (e.g., minimize) the drag area while allowing sufficient space to accommodate a continuous loop (e.g., a belt or chain). In various embodiments, each strut may include an airfoil shape. In various embodiments, any strut (e.g., some struts or all struts) may have a substantially uniform shape along its length. In various embodiments, any strut (e.g., some struts or all struts) may have a shape that varies along its respective length. For example, a strut may taper from a leading edge to a trailing edge, from a wider airfoil (with a higher drag area) to a thinner airfoil (with a lower drag area), or taper in the opposite direction. In various embodiments, any strut (e.g., some or all struts) may have a substantially uniform width along the length of the strut (in the direction of flow). For example, the airfoil may have substantially similar (e.g., equal) chord lengths and / or camber lines along the entire length of the strut. In various embodiments, any strut (e.g., some or all struts) may have a width that varies along the length of the strut (in the direction of flow). For example, the airfoil may have chord lengths and / or camber lines that vary along the entire length of the strut. The struts may have a mirror image shape that is symmetrical with respect to a central axis passing through the strut. Alternatively, each strut may be formed with a shape / contour unique to adjacent struts.

[0037] In various embodiments, each strut may include a separate space configured to accommodate each side of a continuous loop (i.e., the slack side and the tension side). In various embodiments, the separate spaces within any one or all of the vertical struts may be configured to move fluid (e.g., heat transfer fluid) throughout the outboard motor.

[0038] In various embodiments, one or more struts may include a dividing line, thereby dividing the strut into two or more parts. In various embodiments, the dividing line may allow for easy access, thereby enabling the installation or removal of a continuous loop (e.g., a chain or belt) during or after manufacturing (e.g., for repair). The dividing line may extend along the entire length of the strut (e.g., between the nose cone and the anti-ventilation plate).

[0039] Figure 1 shows an isometric view of an outboard motor-type marine propulsion system 100. In various embodiments, the marine propulsion system 100 (e.g., an outboard motor) may include a powerhead section, a motor cowling, a belt drive unit, an anti-ventilation plate, a double strut transmission housing, a lower unit with a propeller, and a skeg. In various embodiments, the outboard motor-type marine propulsion system 100 includes a mount 101 configured to removably connect the transom of the ship to an outboard motor intermediate section 102 via a transom mounting pad 103. In various embodiments, the outboard motor can be steered by various means, including, but not limited to, cables, pulleys, hydraulic actuators, and / or electromechanical actuators. These means are mounted on a steering bracket 104 and rotate the outboard motor about the axis of a steering tube 105. In various embodiments, the angle of the outboard motor and thus the propulsion angle may also be controlled about an inclined axis 106. In various embodiments, the prime mover components are located beneath the upper cowling 107, whether electrically or by liquid fuel. In various embodiments, the side of the cowling 107 facing the transom of the ship may include a faceplate 108. In various embodiments, the drive shaft of the prime mover is connected to the propeller shaft 109 via a synchronous drive belt (not shown). In various embodiments, the synchronous drive belt itself drives the propeller 110, forming a moment to propel the ship to which the ship propulsion system 100 is attached. In another embodiment, the propeller can be replaced with an impeller, water jet, or another propulsion device. In this embodiment, the propeller tail cone 111 and tail fairing 112 are conformed to the geometric contour of the propeller to minimize turbulence losses and maximize efficiency. In another embodiment, the shape of the propeller tail cone 111 and tail fairing 112 may be adjusted to fit different propellers.A sprocket (located within the lower unit) is mounted concentrically to the propeller shaft 109 and housed within the lower unit 114. In various different embodiments, the lower unit 114 may include a nose cone 115 in its front portion. One or more struts 116 provide an open passage for the belt, thereby allowing power to be transmitted from a sprocket mounted to the prime mover below the upper cowling 107 to a sprocket on the propeller shaft 109. The body of a separate strut 116 allows the belt to operate without additional rolling components, enabling the highest possible efficiency. One or more struts 116 are spaced apart so that the belt does not need to be guided around obstacles or profiles, as required in the prior art. The strut body has a hydrodynamic strut leading edge 117 and a strut trailing edge 118, which reduce drag and maximize laminar flow to the propeller 110. The strut 116 is connected to an anti-ventilation plate 120, which is fixed to a bottom collar 121 of the intermediate section. The bottom collar itself is fixed to the bottom of the intermediate section. According to various embodiments, an upper collar 122 of the intermediate section can provide an interface between the intermediate section 102 and the upper cowling 107. In various embodiments, one or more skegs 124 are located on the underside of the lower unit. In various embodiments where two or more skegs are provided, each skeg may be positioned at equal angles around the lower unit 114 and may be located upstream of the propeller.

[0040] Figure 2 shows a block diagram 200 representing the component-level interactions between the propulsion system as a whole and the dual strut lower unit. The component blocks are generally located onboard or offboard and are mechanically or electrically connected as indicated by the legend. In various embodiments, the operator controls the system via a control steering device, which uses onboard communication signals to connect to the energy storage system and additional communication cables to connect to the power electronics offboard. Communication protocols including, but not limited to, serial, CAN bus, SPI, analog, and digital may be used. In various embodiments, the energy storage system is connected to the power electronics block via a DC bus. In various embodiments, the DC bus may range from 12V to over 900V. In various embodiments, the power electronics block generally includes all power stage and control components required to use DC voltage to drive the prime mover. In various embodiments, based on signals from the control steering device, the power electronics can draw energy from the energy storage system via the DC bus to control the prime mover. In various embodiments, the prime mover may be an electric motor powered by phase power and feedback signals. In various embodiments, the prime mover is mechanically coupled to a synchronous belt via a drive shaft. In various embodiments, the belt rotates a driven shaft located in the lower unit, thereby supplying power to the propeller.

[0041] Figure 3 shows a partial side view of the double strut and bullet-shaped structure of the lower unit, generally below the 1-1 line shown in Figure 1. The 1-1 line is, in some embodiments, the waterline of the outboard motor during operation. During operation, all components below the waterline 1-1 are submerged and contribute to the hydrodynamic drag of the system. As described in the background art, stern-drive and outboard-type marine propulsion systems can use a single strut housing connecting the gear case to the powerhead. Additionally, almost all combustion-type outboard motors use a shaft and bevel gear system to transmit power from the combustion or electric powerhead to the propeller. Such types of lower units require a mechanical mechanism for switching between forward and neutral, and neutral and reverse. This type of power transmission requires consistent maintenance for gear lubrication, wears rapidly due to switching at non-zero rotational speeds, and can cause a 15% loss of efficiency. Bevel gears also generate significant noise.

[0042] Recent advances in materials technology have enabled the development of more robust synchronous belt drives. These synchronous belts have the potential to increase efficiency, reduce noise, decrease maintenance, and lower costs. This disclosure enables the use of synchronous belts in marine propulsion systems with a multi-strut body arrangement, in which each side of the belt travels through different struts. Additionally, this disclosure also provides a method for using electronically controlled reversal from an electric prime mover, thereby eliminating the need for complex mechanical switching means.

[0043] In various embodiments, the multiple strut design minimizes fluid flow obstruction to the propeller during motion. In various embodiments, the multiple strut (e.g., double strut) design increases the overall system robustness while reducing the drag-generating frontal area (i.e., drag area). In various embodiments, the interface between the strut 116 and the anti-ventilation plate 120 is integrally formed. In various embodiments, the interface between the strut 116 and the anti-ventilation plate 120 is mechanically fastened (e.g., by bolts and nuts). In various embodiments, the bottom of the strut may be integrally formed with the lower unit 114. In various embodiments, the lower unit 114 may be bullet-shaped (bullet + cartridge case). In various embodiments, the first portion (e.g., tension side) and second portion (e.g., slack side) of the synchronization belt 130 are protected from water and / or external fluids within the space between the first and second struts 116. Therefore, the belt 130 extends (vertically during operation) through the first strut 116 into the lower unit 114, where the belt 130 engages with the propeller 110, driving the propeller 110 (forward / reverse), and extends upward through the second strut 116 back into the cowling 107.

[0044] In various embodiments, drag can be reduced by the hydrodynamic shape applied to the leading edge 117 and trailing edge 118 of the strut 116. In various embodiments, a convex surface on the side of the strut 116 between the leading edge 117 and the trailing edge 118 reduces shape drag and wave formation. In various embodiments, the convex contour does not need to be symmetrical between struts and can be modified for different applications (i.e., the shapes of all struts do not need to be identical). In various embodiments, the struts 116 may be inverses of each other (for example, the first strut may be an inverse of the second strut). In various embodiments, the sides of the struts 116 may be substantially parallel and of equivalent length. In various embodiments, the struts may be non-parallel. In various embodiments, the space between struts may increase or decrease over the height of the struts.

[0045] In various embodiments, the sides of the strut 116 do not need to have recesses. In various embodiments, the front edge 117 may be integrally formed with the strut 116. In various embodiments, the front edge 117 may be manufactured separately and detachably fixed to the strut 116. In various embodiments, the rear edge 118 may be integrally formed with the strut 116. In various embodiments, the rear edge 118 may be manufactured separately and detachably fixed to the strut 116, for example, via strut mounting points (e.g., by screws, bolts, etc.). In various embodiments, the front edge 117 and / or rear edge 118 may be modular and interchangeable to optimize performance. Additionally or alternatively, the strut may include an access panel that allows for belt repair and inspection. The access panel may be spaced apart from the front / rear edge and may be located within a generally flat section of the strut.

[0046] In various different embodiments, the strut may include active control of the surface shape of its leading and / or trailing edges during operation. For example, electronic control (e.g., real-time or manual) may change the camber length or chord length of the airfoil. In another example, electronic control (e.g., real-time or manual) may change the width (e.g., drag area) of the airfoil so that a continuous loop (e.g., a belt) has sufficient room to operate in the space.

[0047] Further reduction of hydrodynamic drag and increased propulsion efficiency are achieved through the overall shape of the structure. In various embodiments, the incoming fluid flow first interacts with the nose cone 115. In various embodiments, the geometry of the nose cone 115 may be geometrically designed to transition smoothly from the nose cone 115 through the nose cone / lower unit interface to the lower unit 114. In various embodiments, the nose cone 115 is removable and replaceable. In various embodiments, the nose cone 115 may include any suitable shape. For example, the nose cone 115 may include a round, bullet-like shape. In various embodiments, the middle portion 113 of the lower unit 114 may have a substantially cylindrical shape (e.g., a cartridge case shape). In another example, the nose cone 115 may be substantially conical with a sharper tip. In various embodiments, as the fluid flow passes through the lower unit 114, the tail fairing 112 can minimize loss-causing boundary layer separation across the tail fairing / lower unit interface, because boundary layer separation causes turbulence and therefore increases pressure drag on the propulsion system 100. In various embodiments, the tail fairing 112 is shaped so that the tail fairing / propeller hub interface hydrodynamically meshes with the propeller hub to optimize the flow entering the propeller. Thus, the strut 116, lower unit 114, nose cone 115, and tail fairing 112 may be constructed in a visually seamless design without abrupt changes in size / shape / diameter, and the assembly of these components forms a continuous outer surface to minimize drag.

[0048] In various embodiments, the tail fairing may be a frustoconical shape tapering from a larger diameter in the intermediate section 113 to a smaller diameter at the propeller 110. In various embodiments, when the propeller 110 rotates and generates high-pressure and low-pressure regions, the flow is directed over the propeller tail cone 111, thereby reducing turbulence and, consequently, further minimizing drag on the propulsion system 100. In a typical combustion marine engine, the engine exhaust is generally directed downward through a single component and outward through the center of the propeller. This disclosure eliminates this type of exhaust and enables a more efficient overall hydrodynamic approach.

[0049] In various embodiments, one or more skegs 124 may be attached to the intermediate portion 113 of the lower unit 114. In various embodiments, the intermediate portion 113 may include one or more skeg mounting points configured to allow the attachment of one or more skegs 124. In various embodiments, the skegs 124 may generally have a fin-like shape. In various embodiments, the skegs 124 may have a constant thickness along their length. In various embodiments, the skegs 124 may have a depth that varies along their length. For example, the skegs 124 may taper from a larger first depth d1 to a smaller second depth d2. In various embodiments, one side of the skegs 124 may be vertical while the other side is tapered. In various embodiments, both sides of the skegs 124 may be tapered. In various embodiments, the skeg 124 may have a curved or airfoil shape, similar to the strut 116. In various embodiments, the skeg 124 is removable and replaceable at the skeg / lower unit interface. In various embodiments, the skeg 124 may be integrally formed at the skeg / lower unit interface. In various embodiments, the skeg 124 contributes to stability and hydrodynamic flow interaction by having a trailing edge that minimizes turbulence in the flow into the propeller 110. In various embodiments, the lowest edge of the skeg 124 may be lower than the blades of the propeller 110, providing protection for the propeller 110 from physical object impacts. Additionally or alternatively, the position of the skeg 124 can be adjusted upstream / downstream relative to the lower unit 114.

[0050] Figure 4 is a partial front view showing generally below the line 1-1 in Figure 1. As shown in Figure 4, the prime mover 128 is rotationally coupled to the belt 130 via a drive shaft (not shown). When the prime mover rotates, either the left side 130a or the right side 130b of the belt 130 can transmit rotational force to and from the propeller. In the illustrated embodiment where the belt 130 rotates counterclockwise (from the viewpoint of the prime mover 128), the left side 130a of the belt is the slack side and the right side 130b of the belt 130 is the taut (i.e., tensioned) side. In various embodiments, the width of the gap between two struts 116 (such as the distance between the inner edges of each strut) can be modified to allow the passage of fluid (e.g., seawater) and to accommodate the dimensions of larger or smaller overall components, while the right side 130b of the belt 130 and the left side 130a of the belt 130 are kept parallel to each other. In various embodiments, the distance d between the inner edges of the strut 116 is gap This can be varied, for example, based on an ideal performance index to reduce the frontal (drag) area. In various different embodiments, the distance d between the outer edges outer This can be varied, for example, to accommodate a thicker pitched belt. In various embodiments, the interface of the strut / lower unit may have a stepped hydrodynamic shape to minimize flow turbulence as water moves through the strut 116 toward the propeller 110. In various embodiments, the propeller 110 may be positioned in front of the strut 116. In various embodiments, an anti-ventilation plate 120 can be connected to the upper part (i.e., the proximal end) of the strut 116 to prevent the propeller from drawing air in from its surface. The anti-ventilation plate can commonly be called a "cavitation plate". The upper end of the strut 116 can be connected directly to the cowling 107. Additionally or alternatively, the upper end of the strut 116 can be connected to a mounting plate / frame that houses the cowling 107.

[0051] Figure 5 shows a partial side view, partially cross-sectional, generally below line 3-1 in Figure 3. In various embodiments, the sprocket 126 is fixed concentrically to the propeller shaft 119, which exits the bullet-shaped portion of the lower unit through the tail fairing 112. In various embodiments, the inside of the lower unit 114 is protected from seawater by seals at all edges and interfaces, including a set of shaft seals. In various embodiments, both leading edges 117 of the strut 116 include coolant passages 117a to allow the passage of coolant. In various embodiments, the coolant enters each strut through the coolant ports and then flows through the coolant passages 117a, which remove heat from the coolant by conduction. Accordingly, the present disclosure provides a closed-circuit fluid cooling system in which the coolant circulation path is confined within struts 116, nose cone 115, and anti-ventilation plate 120. Thus, the coolant system does not need to rely on the intake of ambient water during operation. In various embodiments, one or more coolant passages 117a in each strut allow the coolant to flow into a nose cone space 115a which acts as a thermal barrier reservoir in water. In various embodiments, the nose cone space 115a includes one or more nose cone turbulators 115b (e.g., corrugated structures / walls / strips) configured to increase turbulence of the heat transfer fluid, thereby increasing the thermal barrier capability. Optionally, the coolant passages 117a may extend across the entire anti-ventilation plate 120.

[0052] In various embodiments, the coolant can flow in both directions through the strut 116 and can flow to the heat circuit 140 via the coolant passage 117a. In various embodiments, the coolant passage 117a may have a tube, hose, pipe and / or other fluid transfer method. In various embodiments, the heat circuit may include, but is not limited to, electronic control equipment, pumps and / or power electronics and prime movers, which form heat. In various embodiments, a set of coolant port seals ensures that the heat transfer fluid is not contaminated. In various embodiments, additional spaces that can be used for additional coolant passages may be provided within the trailing edge 118, belt accommodation space 131, tail fairing 112 and / or lower unit 114. In various embodiments, the longitudinal width of the belt accommodation space 131 can be varied for belts of different sizes. In various embodiments, the trailing edge 118 may be mechanically secured by a set of trailing edge fasteners 118a configured for anchoring within an anchor panel 118b (e.g., a T-shaped block). In various embodiments, this mounting method allows the trailing edge 118 to be separated from the strut 116 for installation and removal of the belt 130. In various embodiments, the belt housing space 131 may be optimized so that the size of the space (e.g., the width of the space) is minimized. In various embodiments, from a hydrodynamic standpoint, less space is better (e.g., less drag area). In various embodiments, the belt housing space 131 may be about 1 / 8 inch on each side of the belt 130. In various embodiments, the sprocket gap 125 may similarly have a gap of 1 / 8 inch. In various embodiments, the sprocket gap 125 may be smaller than the space between the belt 130 and the inside of the belt housing space 131, since the belt can only move a little around the sprocket 126.In various embodiments, the belt storage space 131 may have a spacing (e.g., width) between approximately 0.01 inches and approximately 0.25 inches on each side of the belt. For example, if a spacing of 0.25 inches is provided on each side of the belt 130, the total width of the belt storage space 131 will be 0.25 inches + 0.25 inches + belt thickness (in inches). In various embodiments, the belt storage space 131 may include a spacing (e.g., width) between approximately 0.01 inches and approximately 6 inches on each side of the belt. In various embodiments, this spacing may correspond to the system size. In various embodiments, the spacing (e.g., width) may be approximately 12 inches on each side of the belt.

[0053] Figure 6 is a partially cross-sectional top view showing generally below the line 3-1 shown in Figure 3. In various embodiments, the nose cone 115 has an outer contour that maintains an adhering flow (e.g., reducing / preventing boundary layer separation) with a surrounding fluid body. According to various embodiments, the nose cone 115 is conical in shape. According to various embodiments, the nose cone 115 may be blunt or rounded at the tip. In various embodiments, the contour may be modified to suit various operating conditions. In various embodiments, the lower unit 114 may be cylindrical and may be connected to both struts. In various embodiments, the trailing edge 118 may be connected to the strut 116 by fasteners anchored within a T-shaped block 118b. The T-shaped block itself is held in place by the walls of the double strut body. In various embodiments, the leading edge 117 may include a coolant passage 117a having a circular diameter. In various embodiments, the coolant passage 117a may have a substantially constant diameter over the thermal circuit 140.

[0054] Figure 7 shows a partially cross-sectional partial front view generally below the line 3-1 shown in Figure 3. As shown in Figure 7, the lower unit 114 and strut 116 include a belt housing space through which the belt 130 can pass. In various embodiments, the strut 116 includes an inner strut wall and an outer strut wall. In various embodiments, the inner strut wall and the outer strut wall may be formed from any suitable material and may be formed integrally with the rest of the strut body, although this is not required. In various embodiments, the thickness of the strut wall may be selected based on the application, thereby increasing robustness or reducing drag. In various embodiments, within the lower unit 114, the belt-driven sprocket 126 is concentric with the propeller shaft 119. In various embodiments, a keyway 127 is used to transmit torque between the sprocket 126 and the propeller shaft 119. In various embodiments, splines may be used, or the sprocket 126 and the propeller shaft 119 may be integrally formed. In various embodiments, an air-filled sprocket gap 125 is present within the lower unit 114 to accommodate the thickness of the belt 130. In various embodiments, a double strut configuration allows the belt 130 to rotate around the sprocket 126 without physical contact with another part of the lower unit 114. In various embodiments, this contactless operation allows for lubrication-free operation compared to other engines that require the belt or transmission components to operate in an oil-filled bath. The belt 130 can be wrapped around the sprocket 126, engaging each face over approximately 180 degrees of the sprocket's rotation. The sprocket 126 may include raised teeth, as illustrated, which can increase frictional engagement with the belt and generate greater torque.

[0055] Figure 8 is a schematic diagram showing a conventional outboard motor transmission system. In various embodiments, this outboard motor transmission system utilizes a prime mover 807 with a vertically extending drive shaft 808. In various embodiments, power is transmitted from the vertical drive shaft and the horizontal propeller shaft using gears. In various embodiments, a pinion gear 809 is used in conjunction with crown gears 811 and 813 to transmit rotational speed to the driven shaft. In many embodiments, a clutch is used together with a sliding collar 812 that can engage with the clockwise or counterclockwise crown gear. In various embodiments, this mechanism allows for changing the direction of rotation of the propeller shaft while maintaining the direction of drive of the prime mover.

[0056] Figure 9 shows a schematic diagram of a belt drive transmission system. In various embodiments, Figure 9 is a schematic diagram of a specific embodiment for an alternative means of power transmission between a prime mover 901 and a lower driven shaft 905. In various embodiments, the prime mover can utilize a horizontally extending drive shaft 903 to support a sprocket or gear 902 and drive a lower sprocket or gear 906 via a continuous loop 904.

[0057] In various embodiments, any strut may include a nonlinear shape. In various embodiments, to accommodate the nonlinear shape, the belt may remain substantially linear, but the width of the belt housing space 131 (the space between the belt and the inner wall of the strut space) may vary. In various embodiments, the strut may include a pulley (e.g., a roller pulley) configured to form a curve for the belt 130 to follow. In various embodiments, a low-friction pad can be positioned at any suitable location within the belt housing space 131. In various embodiments, any combination of the above three methods can work together to achieve a nonlinear strut shape. In various embodiments, the leading edge of the strut may include a non-uniform contour (when viewed from top to bottom).

[0058] The various components disclosed herein (e.g., struts, nose cones, fairings, skegs) may be formed from a variety of materials, including metals (e.g., aluminum, steel, titanium, etc.), rigid polymers and plastics, wood, etc. In various embodiments, the various components may include composite materials (e.g., carbon fiber, fiberglass, etc.). In various embodiments, the various components may include rubber. In various embodiments, the various components may include thermoplastic resins. In various embodiments, the various components may include any suitable metal-based alloy. In various embodiments, the various components may include materials having high thermal conductivity and high corrosion resistance. In various embodiments, the various components may include one or more coatings (anodizing, powder coating, chemical vapor deposition, paint, etc.). In various embodiments, the various components may be formed from two or more materials (i.e., the nose cone may be mainly aluminum with a rubber-based tip).

[0059] Figures 10A and 10B visualize the computational fluid dynamics of the disclosed double strut (top figure) and a conventional single strut (bottom figure). In various embodiments, this half-body analysis was used to understand the hypothetical hydrodynamic effects and influences of the double strut compared to the single strut. The plots shown in Figures 10A and 10B show laminar flow, as evidenced by the predominantly uniform shading of the fluid flow values ​​(the dark areas in the plot in Figure 10B are above the waterline).

[0060] Figure 11 shows a graphical representation of the initial computational hydrodynamic drag results for the disclosed double strut (left) (approximately 37,500 Newtons over 150 iterations) compared to the conventional single strut (right) (approximately 45,500 Newtons over 150 iterations). This simulation demonstrated the hydrodynamic advantage of the double strut compared to the single strut.

[0061] The descriptions of the various embodiments of this disclosure are presented for illustrative purposes only and are not intended to exhaust or limit the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the embodiments described. The terms used herein have been selected to best describe the principles of the embodiments, their practical application to market-available technologies or technological improvements, or to enable those skilled in the art to understand the embodiments disclosed herein.

Claims

1. A ship's propulsion system, A first strut extending from the proximal end to the distal end and a second strut extending from the proximal end to the distal end, wherein each of the first and second struts has a front portion, an internal belt space, and a rear portion, and the first strut is aligned with the second strut and the first strut is separated from the second strut, the first strut and the second strut, A lower unit connected to the distal ends of the first strut and the second strut, having a nose portion, an intermediate portion, and a tail portion, A sprocket rotatably disposed within the lower unit, A shaft rotatably coupled to the sprocket and concentric with the sprocket, having a front end extending to the front of the sprocket and a rear end extending to the rear of the sprocket, A belt that rotatably connects the drive shaft to the sprocket, wherein a first portion of the belt is located within the internal belt space of the first strut, and a second portion of the belt is located within the internal belt space of the second strut, A thermal circuit extending from the cowling through the first strut and the second strut, respectively, into the lower unit, and having a heat transfer fluid configured to flow through the thermal circuit, A ship's propulsion system that has the following features.

2. The ship propulsion device according to claim 1, wherein the first strut and the second strut have complementary shapes.

3. The ship propulsion system according to claim 1, wherein the space between the first strut and the second strut is uniform over the length of the first strut and the second strut.

4. The ship propulsion device according to claim 1, wherein the thermal circuit is located within the front portions of the first strut and the second strut, respectively.

5. The ship propulsion device according to claim 4, wherein the thermal circuit is bidirectional, passing through the first strut and the second strut, respectively.

6. The ship propulsion device according to claim 1, wherein the thermal circuit further extends through the intermediate portion of the lower unit.

7. The marine propulsion device according to claim 1, wherein the thermal circuit further extends through the tail portion of the lower unit.

8. The ship propulsion system according to claim 1, further comprising plates positioned at the proximal ends of the first strut and the second strut, wherein the plates are substantially perpendicular to the first strut and the second strut.

9. The ship propulsion device according to claim 1, further comprising a propeller coupled to the rear side of the shaft.

10. The ship propulsion system according to claim 1, wherein the lower unit has a nose cone and a tail fairing.

11. The ship propulsion device according to claim 1, wherein the sprocket is located within the intermediate portion of the lower unit.

12. The ship propulsion system according to claim 1, wherein the first strut and the second strut are substantially linear.

13. The ship propulsion device according to claim 1, wherein the first strut and the second strut each have an airfoil shape, the leading edge of the airfoil shape corresponds to the front portion of the first strut and the second strut, and the trailing edge of the airfoil shape corresponds to the rear portion of the first strut and the second strut.

14. The ship propulsion system according to claim 1, wherein at least one strut includes a removable trailing edge portion.

15. The ship propulsion device according to claim 1, further comprising one or more skegs extending from the lower unit.

16. The ship propulsion system according to claim 1, wherein at least one strut and the lower unit are formed as separate components from each other.

17. The ship propulsion device according to claim 1, wherein the thermal circuit forms a closed-circuit fluid path.

18. The marine propulsion system according to claim 1, wherein the distal end of at least one strut is located in the intermediate portion of the lower unit.

19. The ship propulsion device according to claim 1, wherein the internal belt space and the cooling material circuit are separate passages from each other.

20. A ship's propulsion system, A first strut extending from the proximal end to the distal end and a second strut extending from the proximal end to the distal end, wherein each of the first and second struts has a front portion, an internal belt space, and a rear portion, and the first strut is aligned with the second strut and the first strut is separated from the second strut, the first strut and the second strut, A lower unit connected to the distal ends of the first strut and the second strut, having a nose portion, an intermediate portion, and a tail portion, A sprocket rotatably disposed within the lower unit, A shaft rotatably coupled to the sprocket and concentric with the sprocket, having a front end extending to the front of the sprocket and a rear end extending to the rear of the sprocket, A belt that rotatably connects a drive shaft to the sprocket, wherein a first portion of the belt is located within the internal belt space of the first strut, and a second portion of the belt is located within the internal belt space of the second strut. A ship's propulsion system that has the following features.

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